


In Extremis

by thymelord



Category: Doctor Who, Doctor Who (2005), Doctor Who and related fandoms
Genre: (briefly) - Freeform, Alpha/Beta/Omega Dynamics, BDSM, Cheetah!Master - Freeform, Choking, Collars, Dom/sub, Enemies to Lovers, Episode Fix-it: s03e13 Last of the Time Lords, Episode: s03e13 Last of the Time Lords, Face-Fucking, Friends to Enemies to Lovers, Infidelity, M/M, Mating Cycles/In Heat, Non-Traditional Alpha/Beta/Omega Dynamics, Restraints, Rough Sex, Telepathy, why the FUCK is that not a tag that is literally the best trope in the world
Language: English
Status: Completed
Published: 2018-12-22
Updated: 2018-12-22
Packaged: 2019-09-24 13:42:33
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,848
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/17101667
Author URL: https://archiveofourown.org/users/thymelord/pseuds/thymelord
Summary: This is the one aspect of Gallifreyan biology the Doctor doesn’t tell his companions about, and the last thing he thought he would have to deal with when he became the last of the Time Lords.Until he discovered he wasn't actually the last...(A/B/O, on-board the Valiant)





	In Extremis

**Author's Note:**

> NOT going to lie i am Shooketh that there are hardly any doctor who A/B/O or In Heat fics because um?? ALIENS??? ALIEN BIOLOGY?? you could go absolutely buck-wild with that and yet people haven't, what IS this, why are you not all pervs like me i am done

There was something wrong with the Master.

“Not now,” he muttered, turning on the mattress from one side to another so quickly it almost looked like he was having a seizure. “Rassilon’s _balls,_ not now…”

“Sweetheart?” said Lucy, propping herself on her side to look at her husband with concern. “What’s wrong?”

“Nothing,” said the Master through gritted teeth, and Lucy’s frown deepened. The Master was an unparalleled liar; for him to lie as badly as a common human meant that something must be very, terribly wrong.

“Master…” Lucy reached out tentatively, but he shied away from her touch as though it was a burning-hot brand.

“Have to get rid of him,” the Master muttered to himself, as though Lucy wasn’t there. “But I can’t… no. I have to leave… _fuck…”_

“What are you going on about? Get rid of _who?_ The Doctor?”

The effect that name had on the Master was extraordinary. He leapt out of bed and grabbed his dressing gown almost in the same motion and stood by the side of the bed, drawing the robe around him and trembling. He looked up at her, and Lucy could have sworn she saw a glimmer of green in his irises. But before she could be sure, the Master turned on his heel and ran, door slamming so hard the entire _Valiant_ seemed to shake.

~

The Doctor dozed in and out of sleep and wakefulness, being in a state of both and neither simultaneously, and when he saw a haggard-looking Master in a pastel-pink silk dressing gown pointing a laser screwdriver at him through the bars of the door, he thought it must be part of a dream. This illusion was quickly dispelled when he was hit by an excruciating bolt of energy from the screwdriver. Every single cell in his body was on fire, his nerve cells in particular feeling like they were made from molten metal. He raised his head, peering up at the Master from where he was splayed out on the floor of his cell. For a moment, the Doctor thought he had been aged even further, but to his surprise he found he was back to his young self again. He was relieved for a moment, before he realised that the Master must have some sort of ulterior motive – and seeing his cheetah-slit eyes and elongated canines, he realised what it must be.

It didn’t take them very long after the Cheetah world to figure out that the virus had left an indelible mark on the Master, a few latent shreds of virus clinging onto his DNA in a way that was so tenacious, it appeared to have even survived through regeneration.

At first, it didn’t seem like the virus did anything much, except from make his eyes look slightly cat-like every now and again, but in time it came abundantly clear that there was one aspect of Cheetah biology that was extremely similar Gallifreyan biology, and that the virus seemed to amplify it.

The Master unlocked the door with trembling hands, and then just stood there, framed in the doorway, staring at him with wide, vivid-green eyes. The Doctor hesitantly got to his feet, pressing against the back of the cell. He took a very small step forward, extending his hand tentatively  towards him. “Master,” he said softly. “Master, I can help you.”

“No,” snarled the Master in a very feline-like way. “I don’t want your help. I don’t _need_ your help.”

“Then why did you come?”

The Master was silent, eyes narrowing infintessimally. “I can’t… I refuse to be beholden to…”

The Doctor advanced until he was close enough to lay a gentle hand on his arm. The Master flinched, but didn’t pull away. “Biology doesn’t mean anything,” said the Doctor. “You can…” The Doctor swallowed, closed his eyes, and briefly wondered what the entire fuck he was doing. Had, perhaps, _he_ been infected with a speck of that Cheetah virus so long ago, or was this what every omega-triggered alpha heat was like? He’d forgotten the feeling; it had been so long since he’d been in contact with another Time Lord in heat, let alone an omega.

“You can do anything you want with me,” the Doctor said. “Please. _Master._ My Master, please - ”

The Master gave a sharp intake of breath, and grabbed the Doctor’s arm, pulling him out of the cell and throwing him against the wall. The pain jolted down his spine, seeming to intensify the storm of arousal within him. “Say that again,” said the Master.

The Doctor let out a long breath. “You heard what I - ”

The Master backhanded him across the face. “Say it again.”

“Master,” gasped the Doctor.

“There was a little bit more,” purred the Master, one of his pointed canines dangerously close to the Doctor’s throat. “Wasn’t there, Theta?”

“My Master,” whispered the Doctor.

“And do you know what that makes you?”

The Doctor shook his head minutely, taking care not to get too close to the Master’s fangs.

“Mine,” snarled the Master. “You are _mine,_ Theta.” He grabbed the Doctor’s shirt, tearing it off him with a vicious strength that both frightened him and turned him even further on. He tugged at his belt buckle, slowly sliding it off before removing the rest of his clothes. He closed both hands around the belt, snapping it between them. “Multi-purpose garments, hmm? My favourite sort.” The tip lashed out, catching the Doctor across the chest. 

He gave a soft moan, head falling backwards. Somewhat strangely, perhaps, the only torture the Master had inflicted on him on the _Valiant_ was his aging, and subsequent de-aging, by the Lazarus Technology-enhanced laser screwdriver, and to his horror… he was _craving_ it. He was craving for the Master to hurt him, for that exquisite edge of pain that curled around the periphery of his pleasure, intensifying it and bringing it to heights that it could never have achieved without it.

And the Master didn’t have to throw up a psychic connection to know everything that had just flashed through the Doctor’s mind.

A predatory smile came over the Master’s face. Even normally, the Master’s predatory looks were something to behold, but with those fangs…

“Oh, Theta. Are you sure _you’re_ not the omega?”

“Don’t be essentialist,” said the Doctor. “Unless you _want_ to be essentialist, hmm?” In a flash, the Doctor had pushed the Master to the floor, his hand hovering over the gland at the side of the Master’s neck that all omegas had, that would make him turn into a writhing, begging mess. Fury flickered in the Master’s eyes, and he actually let out a _growl,_ switching their positions so the Doctor was pinned beneath him.

“How dare you.” The Master’s voice was quiet and low, which somehow seemed even more dangerous than if he was screaming at him. “ _How dare you.”_

The Doctor shivered beneath him as the Master pressed down on his Adam’s apple. His legs spread slightly in anticipation, hips canting upwards.

The Master cast his dressing-gown aside, but not before pulling out a penknife from his pocket. He was only wearing a pair of tight black boxers beneath, and the Doctor didn’t know if he was more aroused by that or by the blade that the Master had just flicked open.

Much like the Master’s other incarnations, he had a lean but soft abdomen, muscles only lightly defined. With most of his other incarnations, he’d had a dark line of hair running upwards from his groin and sometimes connecting to bushy curls on his chest; this new regeneration had light, sparse hair, and for whatever reason, the novelty excited him.

But the Doctor didn’t have much time to admire his form before the Master was very lightly tracing the razor-sharp tip of the blade along the Doctor’s bottom lip. His lips parted by a millimetre, breath clouding on the metal. The tip of his tongue shot out and ran along the flat side of the knife.

“You are playing with fire, little Theta.” The knife trailed down, resting on his throat. “I could slit your throat right now, force you to regenerate. Perhaps I could do it while I fuck you, That would be fitting, don’t you think? The biggest slut Gallifrey has ever known, regenerating a cock up their arse. Then you really would belong to me, wouldn’t you?”

“I already belong to you, Master,” whispered the Doctor. “It would be your prerogative to do that, sir. Your _droit du seigneur._ ”

The Master’s eyes widened, and the Doctor felt him harden even further against his thigh, something which seemed nigh impossible.

“Master, please…” The Doctor tugged insistently at the waistband of his boxers. “I need…”

“Do you want to see my cock, my little whore? Do you _need_ it?”

“Y-yes,” whimpered the Doctor.

The Master slowly pushed his underwear down his hip, before throwing it into the corner of the room. The Doctor let out a shaky breath that bordered on a gasp, pupils dilating so much that his hazel irises were almost completely swallowed.

The Master smirked. “Like what you see?”

He did. Omegas were smaller on average than betas and especially alphas, but the Master had always been more beta-length – but _this_ one would have been large even for an alpha. The Doctor felt a swamping, almost atavistic urge to close his lips around that thick shaft, taste the beads of pre-cum sparking with artron energy…

“Poor darling,” cooed the Master, stroking his hands through the Doctor’s hair as though calming a wild animal. “It’s been so many centuries since you’ve had me, and you really are a _mess,_ aren’t you?”

The Doctor made a wordless, desperate noise in the back of his throat.

“Come on then, pretty boy.” The Master stood up, and hauled the Doctor to his knees.

The Doctor looked up at him with those brown, brown doe eyes. He knew the Master’s current gentleness would be followed by him forcing his cock down his throat, and the Doctor felt a frisson of excitement go through him.

He took the Master in his mouth, that familiar musky taste making him moan a little around his shaft. He had been with very few other people other than the Master, despite having lived over nine hundred years, but that small handful had not tasted anything like the Master.

Sometimes he thought they must have accidentally bonded all those years ago back at the Academy, because how else would the Master have such a hold over him? Why else would he feel like a Gallifreyan in his first heat every time he was with him?

Perhaps it was just the effect of being in heat. Everyone took heat suppressants, except from perhaps the Shoboggans, and it was considered incredibly crass and uncivilised – not to mention inconvenient - to allow your heats to run their natural course in public. However, they didn’t trigger unless you were within pheromone-detecting distance of another Gallifreyan, and the distance itself was shortest for alphas and omegas, and longest for same-status individuals. Suppressants had been rendered ineffective for the Master after the Cheetah virus, and the Doctor hadn’t bothered taking his since the destruction of Gallifrey.

A recipe for disaster.

The Master let out a soft sigh. “ _Ah…”_

The Doctor extended the thread of a telepathic link, just a little bit, just enough to speak telepathically but not for them to see into each other’s thoughts. He was surprised he managed to do it; he found it difficult at the best of times, let alone when the Master was five inches down his throat.

The Master accepted it, a smile tugging at the corner of his mouth. “ _Something you wanted to say?”_

“ _You’re delectable.”_ The Doctor emphasised this statement with a lick from base to tip, tongue playing with the edge of his foreskin. The Master whined, and the Doctor’s eyes flicked up in surprise and pleasure, delighted that his composed façade was finally beginning to crack. The Doctor wanted him as wild as he’d seemed when he’d first come to him, addled with pheromones and heat, swollen and dripping and _begging._

The Doctor wasn’t afraid to make him come; the refractory period for omegas in heat was outrageously short. Well, for any Gallifreyan in heat, really.

Suddenly, the Master grabbed him by the back of his hair, holding his head still as he shoved into his throat to the hilt. The Doctor choked, and for a moment he thought he wouldn’t be able to stand it, but even as his throat convulsed the Master held him there. The Doctor looked up again, eyes streaming.

“Beautiful,” whispered the Master, and pulled out so only the tip of him was resting on the Doctor’s lips, before thrusting back inside with a fast, brutal motion. The Doctor let out a muffled scream as the Master continued to fuck his throat, using him like a doll, a fleshlight, an object that had no purpose except for its Master’s pleasure.

The Doctor’s hand crept towards his cock, hoping the Master wouldn’t notice, but naturally…

“No,” said the Master sharply. “If you dare touch yourself, I swear to Rassilon I will put you in a cock cage and fuck you over and over again, until you’ve never been so desperate in your life but you won’t. Be. Allowed. To. _Come._ ” The last words were punctuated by an even more vicious thrust into his throat, hand so tight in the Doctor’s hair it was though he was trying to pull it out. “Do you understand, slut?”

“ _Yes, Master,”_ The Doctor sent through their link. _“I’m sorry, please don’t, please - ”_

“Didn’t you say I could do what I liked with you?”

“ _Not that,”_ whined the Doctor. “ _You can’t, you can’t - ”_

“I won’t,” soothed the Master. “Just do everything I say. Everything. Because you are _mine!”_

“ _Yours,”_ agreed the Doctor.

The Master didn’t warn him when he came, that beautiful, salty-musk fluid sliding down his throat. He swallowed it all eagerly, a litany of moans pouring from him. When the Master finally let him go, he slid to the floor and gasped for air with almost as much fervour as he’d drank down the Master’s release.

The Master kneeled down, petting him gently. “I wonder… what shall I do to you now?”

The Doctor merely looked, smiling patiently. Out of nowhere, the caress turned into a slap, the force making his other cheek hit the floor. The Doctor let out a shuddering breath. “Wh-why…”

“I just gave you this wonderful treat,” said the Master, “something that a slut like you doesn’t deserve, and what do you do? You don’t even thank me.”

“I’m sorry, my Master, I’m sorry… thank you, thank you for giving me your cock…”

“You’re forgiven, if only because you did such a wonderful job. In fact…” The Master hauled him to his feet, and he stumbled slightly, a tiny bit dizzy from arousal. “Shall I give you another treat? We can go to my bed. How would you like that, hmm? Would you like to be fucked on a feather mattress, slut?”

“Yes, Master. Thank you, Master.” The Doctor bit his lip. “But your wife…”

“Lucy won’t mind,” said the Master in a clipped voice. “I’ve never slept with her, you know. Whenever she wants to I always hypnotise her to sleep.”

The Master retrieved his robe from the floor and donned it, and then picked up the belt. He secured it around the Doctor’s neck – to his delight, it was the sort that had holes all the way round, so he could make it small enough – and clasped the other end in his hand. He tugged the Doctor along to the bedroom, the latter still completely naked with his swollen erection standing nearly flush against his stomach. When he threw the door to his bedroom open and snapped “Out,” Lucy only looked a little bit surprised. Mostly, she was just resigned.

She’d barely slammed the door shut when the Master was tying the other end of the belt to the headboard. “So beautiful,” he hummed, stroking the Doctor’s reddened cheek. His dressing gown slid to the floor, and the Doctor saw that he was already hard again. The Doctor spread his legs invitingly, baring his puckered arsehole, but didn’t dare ask in case the Master took it as a sign of subordination and clapped his cock in a cage. He couldn’t, however, stop a little whine from escaping him.

“You’re gagging for it,” said the Master admirably. “My alpha toy, dying for his omega’s cock. Begging to be pounded insensate.”

The Doctor nodded fervently, the makeshift collar tugging at his neck. The Master ran a finger around the rim of his entrance, and his eyes widened. “You’re so wet,” he breathed. “There’s a myth that alphas can’t get wet, but you can. Just not as wet as a beta or omega. _You_ though, you’re as wet as an omega. An omega _whore.”_ He rubbed the head of his cock over his slick entrance, and the Doctor whimpered. He breached him suddenly, the Doctor’s wetness enough for him to enter him but not enough to ease the pain. The Doctor’s back arched involuntarily, hips canting upwards to meet the Master’s thrusts. He was tempted to rake at his back, but was afraid the Master would see that as a dominant gesture, so instead he gripped the sheets – silk, of course – so tightly his knuckles turned white. The Master grabbed the belt and pulled it, choking him.

There was nothing quite like having one’s air cut off. It was the pain that potentiated pleasure, but it was more than that – the act itself felt tenfold more pleasurable than painful, a cocktail of adrenaline and endorphins that took his soul to celestial heights. He could feel his respiratory bypass kick in, and for one terrifying moment he thought the Master would fulfil his promise to fuck his regenerating body; but then he let go, and the Doctor took in gulps of air.

The Master’s hand hovered over the Doctor’s cock, and then moved upwards to his nipple, pinching it sharply between his thumb and forefinger. The Doctor’s eyes rolled backwards, and he was so overcome that he couldn’t even meet the Master’s thrusts, but just lie there lost in his pleasure.

The Master let out a sharp gasp, and then he was filling the Doctor with his cum, pulling his leash again. The Doctor was still limp with pleasure, and barely reacted as the Master undid the belt and threw it to the floor. The Master regarded him through burning eyes, and a shiver shot through the Doctor as he saw the look on his eyes.

“I want you to take me,” said the Master, the tiniest tremble of uncertainty in his voice. “Take me, fuck me, _wreck me,_ but remember that I control you. You’re doing this under _my_ order.”

“You want me to fuck you?” said the Doctor in a ragged voice. “You want me to pump your lovely little hole, want me to come inside you?” The Doctor flipped them so the Master was pinned beneath him, his light brown hair in disarray, energy already returning. The Doctor leaned down, lips brushing his ear. “Do you want my knot? You want to be _bred?”_

The Master whined, legs spreading as far as he could. His position was that of a classic omega, and yet the steel in his gaze reminded the Doctor who was really in charge – and that he wouldn’t hesitate to punish him if he put a toe out of line. “Knot me,” agreed the Master. “Br-breed me. _Now!”_

The Doctor complied, fucking into him slowly, gently. The Master let out a groan of impatience. “Fuck me like you mean it,” he whined. “Take me roughly, u-u-use me… fuck. _Use_ me, Theta Sigma, _use me!”_

“As you wish, Master.” He began fucking him so hard the Master’s head hit the headboard, and the Doctor winced; but the Master was so far gone he didn’t even seem to notice. His breaths came in tiny, high-pitched moans, and his legs wrapped around the Doctor’s hips like a vice.

“Harder,” gasped the Master. “ _Harder!”_

“I might hurt you if I - ”

“ _Then hurt me!”_

The Doctor’s hand circled the Master’s throat. “Do you want me to…”

“Yes! Choke me, hurt me…”

This was something the Doctor had always loved about sex with the Master: although the Master was obviously the more dominant one, they were both extremely versatile, and the Master often wanted to be dominated as much as he wanted _to_ dominate – as long as the Doctor remembered who was really in charge.

The Doctor’s hand pressed down, and the Master let out a gasp, nails biting into the Doctor’s back so hard he drew blood. His hips pushed upwards, forcing the Doctor’s cock inside him to the hilt. The Doctor let out a gasped moan, and released inside him. The Master let out a high-pitched, primal whine as he felt the Doctor’s cum flood him, his cock swelling within his arse. The Master’s head fell backwards, face contorted with ecstasy. “Oh…”

“It’s been so long for you, hasn’t it?” said the Doctor, softly caressing his cheek. “So long since you’ve been knotted.”

“There’s been no one… no one except you,” the Master admitted. He whimpered again, clenching around the Doctor’s knot.

“Ah, love… how long was it, for you?”

“Millennia uncountable,” sighed the Master.

“Something tells me you’re lying.”

“Well it feels like that,” said the Master petulantly. He twitched beneath him, arms clasping around his torso. He felt the knot start to deflate, and reflexively clenched harder, rolling them over and pushing down on him desperately.

“Haven’t had enough?” teased the Doctor.

“Never,” breathed the Master. “I could never have enough of you.”

“So,” said the Doctor quietly as the Master slid off him, laying his head on his chest. “What happens now, Koschei?”

The Master huffed a soft laugh against his skin. “Ah… I wish I knew.”

“Restore my TARDIS. Come with me.”

“Previously, I would have called you insane. And maybe you are, but it seems that I have joined your particular… brand of insanity.”

“Any reason why?”

“The drums,” said the Master simply. “They were quiet, for a moment…”

“Travel with me, and perhaps they’ll disappear.”

The Master swallowed “How do you put up with me? How do you still want to be my friend, after everything I’ve done? After everything I’m _still_ doing?”

“Because I believe you have the capacity to change. Not just that, but I think you _are_ changing.”

The Master gave a surprised laugh. “What?”

“Why else would you use a paradox machine? It could be reversed like _that._ Everything you’ve done, gone.”

“Not everything,” said the Master quietly.

“Besides, it seems I’m hopeless. An absolute idiot. Because even at the final hour, in the deepest pit, without hope, without witness, without reward… I love you.”

The Master let out a sob, and the Doctor’s arms tightened around him.

**Author's Note:**

> how many times am i going to write a version of the doctor and the master reconciling on the valiant? ONE HUNDRED THOUSAND. and perhaps even more. 
> 
> also, this isn't the last you've seen of me and my Time Lords in Heat fics.... mark my words


End file.
